9 

 in great excess of the numbers of larvae found later in the same plots. Sub- 

 stantiation of these observations has been sought bv laboratory tests. 



In these tests Black-leaf " 40 " at the strengths of 1-100 and 1-250 killed all 

 the eggs which were not parasitized. It is interesting to observe that Black- 

 leaf "40 " does not destroy the egg parasites. Parasitized eggs included in 

 the experiments vielded the adult wasps even when sprayed with the greatest 

 strength of Black-leaf " 40 ". 



Recommendations. — The experiments here recorded indicate that almost 

 complete relief from squash vine borer attack can be gained by four applica- 

 tions in July of Black-leaf " 40 " at a strength of 1 part in 100 parts of water, 

 where the applications are made with a power sprayer. At the same strength, 

 the material is over 90 per cent effective applied with a low-pressure, small- 

 capacity outfit such as the compressed air sprayer. Applied at a strength 

 of 1 part in 250 parts of water with the aid of a power sprayer, the material 

 is also over 90 per cent effective. Lead arsenate gives too small a percentage 

 of control to warrant its use.* 



On the basis of the experimental evidence, the following recommendations 

 are made for the use of nicotine sulfate against the squash vine borer. 



1. If a compressed air sprayer, knapsack pump, or other small capacity, 

 low-pressure outfit is to be used, apply Black-leaf " 40 " at the rate of 1 part in 

 100 parts of water (1.3 fluid ounces per gallon) making 4 applications, one 

 week apart in July. 



2. If a machine capable of maintaining a pressure of 100 to 150 pounds per 

 square inch is to be used, such as a good barrel pump or a power outfit, apply 

 Black-leaf " 40 " at the rate of 1 part in 250 parts of water (3.2 pints in 100 

 gallons), making 4 applications, one week apart in July. 



3. In spraying, be sure to drench all sides of the stem at the base. See that 

 the leaf-stalks, and the under and upper sui'faces of the leaves are thoroughly 

 sjDrayed. When the plants have started to run, it is hardly necessary to spray 

 the runners beyond three or. four feet from the center of the hill. 



4. Thorough spraying will largely free the sprayed fields from borers. Ex- 

 termination may then be made complete by an examination of the plants in 

 mid- August, cutting out those borers that have escaped the spray. 



Spraying may be begun during the first week in July. It would be better, 

 however, to examine a few plants closely every day during the last week in 

 June, in order to discover the fii'st eggs. The first spray should be applied not 

 later than a week after eggs are discovered. 



Cost of Treatments Versus expected Profits. 



Nicotine sulfate is a relatively expensive insecticide, and any spraying oper- 

 ation using this material at a strength of one part in one hundred parts of 

 water, or one part in tAvo hundred fifty parts of water, is a costly treatment, 

 which will be quite likely to i^rove impractical under certain conditions of 

 squash culture (i.e., where the squash vine borer is not a serious pest). 



The expense of treatment can be materially reduced by following the sug- 

 gestions given below. 



1. To facilitate spraying squashes, plant in wide roAvs Avith the hills close 

 together in the roAv. This type of planting alloAvs free passage of the spray 

 rig betAveen the roAvs, and little time is lost in stepping from hill to hill. 



2. Thin to the desired number of plants in each hill as early as is compatible 

 with good farm practise. In this Avay, no spray material is Avasted on plants 

 that are later to be destroyed. 



3. Equip the four- foot spray rod Avith a 45° angle disc nozzle Anth a small 

 hole in the disc. This breaks the spray up into a \'ery fine mist Avhich eoA'ers 

 quickly and thoroughly Avith a minimum of waste. In addition, equip the base 

 of the spray rod Avith an automatic shutoff of the spring-grip type, so that 

 the stream can be stopped instantly, thus alloAving no Avastage Avhen passing 

 between hills. This type of equipment can be used as Avell Avith a compressed air 



